\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=0.7]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw[->] (-1,0)--(11,0)node [right]{$\omega t$};
  \draw[->] (3.1416/6, -1.5)--(3.1416/6, 2.5)node [above]{$i,u$};
  \foreach \x in {3.1416*7/6, 3.1416*13/6, 3.1416*19/6}
  {
     \draw (\x, -.1)--(\x, .1);
  }
  \draw [ultra thick] plot[domain=0:3*3.1416, samples=1000] function{1.5*sin(x)} ;
  \draw[dashed](0,-1)--(0,0);
  \node at (3.1416/12, -.5){$\phi_0$};
  \node at (3.1416/12, -2){$\phi_0=\pi/6=30^{\circ}$};
  \draw[->] (-.5,-.5)--(0,-.5);
  \draw[->] (3.1416/6+.5,-.5)--(3.1416/6,-.5);
  \node at  (3.1416/6+.25,.25) {$O$};
\end{tikzpicture}
\end{document}